Biliary excretion of olmesartan, an anigotensin II receptor antagonist, in the rat

Background and Aim: Olmesartan (RNH‐6270) is a newly developed anigotensin II receptor antagonist, and has been reported to be excreted into feces. To examine the mechanism of the biliary excretion of olmesartan, we studied its biliary excretion in rats. Methods: The biliary excretion of olmesartan in Eisai hyperbilirubinemic rats (EHBR), a multidrug resistance protein 2‐deficient rat, was compared with control rats, and the effect of organic anions and cation and bile acids on the biliary excretion of olmesartan was studied in control rats. Results: The biliary excretion of olmesartan was markedly delayed in EHBR. The biliary excretion of olmesartan was inhibited by sulfobromophthalein, cefpiramide and pravastatin, but was not inhibited by taurocholate or tauroursodeoxycholate. Vinblastine inhibited and phenothiazine treatment increased the biliary excretion of olmesartan. Conclusions: These findings suggest that olmesartan is excreted into the bile mainly by multidrug resistance protein 2 and partly by P‐glycoprotein.